Conjugated fatty acid represented by conjugated linoleic acid (CLA) has been reported to have various physiological activities such as a lipid metabolism improving effect, an anti-arteriosclerosis action, a body fats decreasing action and the like (non-patent documents 1-3), and is a functional lipid expected to be applicable to various fields of medicament, functional food and the like (patent documents 1, 2). While CLA is known to be contained in dairy products and meat products since it is produced by microorganisms present in the stomach of ruminant and to be present in a small amount in vegetable oil, the detailed mechanism of production thereof is not known.
The present inventors reported that 3 kinds of enzymes present in the fungus body of Lactobacillus plantarum (CLA-HY, CLA-DC, CLA-DH) are essential for the reaction to convert linoleic acid to conjugated linoleic acid (patent document 1). However, the mechanism of a series of specific reactions, the presence of an intermediate and the like in these enzyme reactions have not been clarified.
In addition, it has been reported in recent years that oxo fatty acids such as 9-oxo-octadecadienoic acid, 13-oxo-octadecadienoic acid and the like contained in tomato have an activity to improve lifestyle-related diseases, such as lipid metabolism improvement and the like (patent document 3, non-patent documents 4, 5), and the physiological activity of oxo fatty acid is drawing attention. While oxo fatty acid has a carbonyl group at a particular position of unsaturated fatty acid, synthesis of functional oxo fatty acid from unsaturated fatty acid is difficult since it is necessary to distinguish double bonds present in a plurality in a molecule and introduce carbonyl group into a particular position. Also, it is not known that rare fatty acids such as CLA1, CLA2 and the like are produced from a particular oxo fatty acid.